Previous studies from our laboratories indicate that TSH as well as FSH can induce morphological alterations and ABP secretion in Sertoli cell-enriched cultures. These responses are not a result of TSH contamination since an equal or 5-fold dose of LH (which contains a similar amount of FSH contamination as does the TSH preparation) does not induce a similar response. The objectives of the experiments of this proposal are to investigate the mechanisms by which TSH affects the biochemistry and morphology of Sertoli cells in vivo and vitro. Specific aims of this proposal are: 1) to determine if radioiodinated TSH binds specifically to Sertoli cells in vitro and in vivo, 2) to determine if TSH induces c-AMP accumulation in vitro, 3) determine if TSH can affect protein synthesis and messenger RNA synthesis in vitro and in vivo, 4) determine if TSH regulates ABP secretion in vivo, and 5) determine if TSH and FSH have synergistic or antagonistic effects on morphology changes similar to those seen in the testis of hypophysectomized animals. Although numerous studies have been conducted to determine the role Sertoli cells play in spermatogenesis, the mechanisms involved in this process remain obscure. The Sertoli cell culture system provides an excellent model to study the direct action of hormones on this cell type. This proposal provides experiments to compare in vivo and in vitro hormone-induced events, thus, further testing the validity of the Sertoli cell culture model as well as providing new information on the regulation of Sertoli cell structure and function in vitro and in vivo. The information that will result from the studies of this investigation may provide a basis for further studies to develop more effective procedures for the treatmnt of infertility. This information may also aid additional studies designed to develop feasible male contraceptive procedures.